Magnetoresistive sensor including magnetic domain control layers having high electric resistivity, magnetic head and magnetic disk apparatus

ABSTRACT

There are provided a magnetoresistive sensor of the type of flowing a signal sensing current perpendicular to the plane to improve resolution at reproducing a signal, a magnetic head using the magnetoresistive sensor, and a magnetic disk apparatus. 
     A magnetoresistive sensor comprising a substrate, a pair of magnetic shield layers consisting of a lower magnetic shield layer and an upper magnetic shield layer, a magnetoresistive sensor layer, disposed between the pair of magnetic shield layers, an electrode terminal for flowing a signal current perpendicular to the plane of the magnetoresistive sensor layer, and magnetic domain control layers for controlling Barkhausen noise of the magnetoresistive sensor layer, wherein the magnetic domain control layers disposed in contact with opposite ends of the magnetoresistive sensor layer consist of a material having high electric resistivity and with a specific resistance not less than 10 mΩcm so as to give the magnetoresistive sensor having excellent reproducing resolution. The sensor is used to provide a magnetic head having excellent reproducing resolution and a magnetic disk apparatus.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional of U.S application Ser. No. 09/811,606 filed 20Mar. 2001, now U.S. Pat. No. 6,870,718, issued on Mar. 22, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetoresistive sensor includingmagnetic domain control layers for the magnetoresistive sensor forreading back magnetically recorded information, a magnetic head, and amagnetic disk apparatus. More specifically, it relates to amagnetoresistive sensor having excellent reproducing resolution, amagnetic head using the same, and a magnetic disk apparatus.

2. Description of the Related Art

The recording density in a magnetic disk apparatus has been improvedsignificantly, and the demand that the performance of the magneticread/write heads thereof be enhanced is increased in regard to bothcharacteristics of read and write.

Regarding the read head sensor, it is necessary to improve thetechniques concerning three points: (1) improvement of a technique formaking the efficiency higher, (2) improvement of a technique for makingthe track width smaller, and (3) a technique for making the gap betweenthe write magnetic shields smaller.

With respect to (1), making the efficiency higher has been advanced bydeveloping an MR head utilizing a magnetoresistive effect. At a lowrecording density of several giga bits per square inch (Gb/in2),anisotropic magnetoresistive effect (AMR) is used to convert themagnetic signal on recording media to an electric signal. At a highrecording density exceeding this, a higher efficient giantmagnetoresistive effect (GMR) is used to respond to this high recordingdensity. However, when making the efficiency much higher is advanced,the structure must be changed to the perpendicular magnetic recordingstructure in relation to the read element, which makes the most of GMR(CPP-GMR) or a tunnel magnetoresistive effect (TMR) of a system forflowing a sensing current perpendicular to the plane.

As a known example of a magnetic head employing GMR, Japanese PatentPublication No. Hei 8(96)-21166 (Japanese Un-examined Patent PublicationNo. Hei 4(92)-358310) describes the structure called a spin valve. Thiscomprises a pinned layer consisting of a magnetic material in which aanti-ferromagnetic layer pins magnetization in the specific direction,and a free layer consisting of a non-magnetic thin film laminated on thepinned layer and a magnetic layer laminated through the non-magneticthin film, so as to change electric resistance at a relative angle ofmagnetization of the pinned layer and the free layer.

With respect to (2), the track width is made smaller to improve thetrack density. It is generally thought that the read track width isdetermined by the distance between electrodes flowing a sensing currentfor sensing changed resistance. The read sensor has a high loss of S/Nwhen Barkhausen noise is caused, and it is necessary to control this.The Barkhausen noise is caused together with microscopic domain wallmovement, and there must be arranged magnetic domain control layers soas to provide the read sensor singly in the form of a magnetic domain.The magnetic domain control layers are often arranged on opposite sidesof the sensor layer portion of the read sensor, viewed from themedia-opposed surface side. The magnetic domain control layer isgenerally a hard magnetic metal material layer formed on a suitablemetal underlayer, and an insulating oxide layer is required for thecontact surface of the same with the magnetoresistive sensor layer, thetop surface of the lower shield, and the contact surface of the samewith the upper shield. The magnetic domain control layer provides amagnetic field for the magnetoresistive sensor layer, so that theanisotropic magnetic field is increased effectively and the exteriormagnetic efficiency is reduced greatly. For this reason, JapaneseUn-examined Patent Publication No. Hei 9(97)-282618 describes thestructure in which the gap between the electrodes is smaller, than thatbetween the magnetic domain control layers, and a sensor region havingan efficiency effective for the exterior magnetic field is used forsensing a signal.

With respect to (3) the technique for making the read gap smaller, thatis, for making the gap between the read magnetic shields smaller, therehas been studied improvement of linear recording density by modifyingresolution. Generally, the shield layers are arranged at the upper andlower sides so as to interpose the magnetoresistive sensor layer, and agap layer made of an insulating material is disposed between the shieldlayer and the magnetoresistive sensor layer so as to prevent a sensingcurrent from being leaked to the shield. When the gap between the readmagnetic shields is smaller, the thickness of the gap layer is reduced.Thus, the thickness dependence as the characteristic of the insulatinglayer or the presence of pinhole cannot maintain the insulatingproperties, so that an electric current for sensing a signal (sensingcurrent) is leaked to the magnetic shield to reduce read output. Thisloss is called a shunting loss.

As a method of solving this, Japanese Un-examined Patent Publication No.Hei 5(93)-266437 describes the structure in which an insulating magneticlayer is arranged on the surface of the magnetoresistive sensor layerside of at least one of the magnetic shields.

The read element is difficult to provide a sufficient recording magneticfield in a conventional in-plane magnetic recording system. Further, CPP(Current Perpendicular to the Plane)-GMR or TMR as a high efficientmagnetoresistive sensor is a magnetoresistive sensor utilizing astructure flowing a sensing current perpendicular to the plane. Thus, afuture structure of the read element is thought to be of the CPP systememploying a sensing current. However, employing such a structure, whenthe area of the magnetoresistive sensor layer is reduced, there arises anew problem that the conventional magnetic domain control layer isdifficult to ensure the insulating properties of the magnetic domaincontrol layer. In other words, the conventional magnetic domain controllayer is arranged on the lower magnetic shield by employing a laminatingstructure of insulating layer/(metal underlayer)/hard magnetic metalmaterial layer/insulating layer, and then is in contact with oppositeends of the magnetoresistive sensor layer. The magnetoresistive sensorlayer is made thinner and finer; there are imposed three problems: (1)the throwing power of the lower insulating layer is insufficient so asto shunt the sensing current flowing to the magnetoresistive sensorlayer to the magnetic domain control layer, resulting in reduction ofoutput, (2) the thick lower insulating layer is adhered so as toincrease the gap between the magnetoresistive sensor layer and themagnetic domain control layer, thereby making the magnetic domaincontrol different from the design, and (3) in consideration of thethickness maintaining the pressure resistance of the insulating layer,the magnetic layer thickness of the magnetic domain control layer isreduced relatively, so as not to ensure a predetermined susceptibility,thereby making it difficult to design the magnetic domain control.Further, when employing the yoke structure or the flux guide structureof the TMR element, these must be magnetic domain controlled. Simply,there is employed means for laminating a plurality of theabove-mentioned magnetic domain control layer. This will involve a verydifficult problem in process.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a magnetoresistivesensor having, in particular, excellent reproducing resolution, inmagnetic read and write, a magnetic head using the same, and a magneticdisk apparatus, and, for that, to provide magnetic domain control layershaving high electric-resistivity suitable for improving the reproducingresolution of the magnetoresistive sensor.

In order to achieve the foregoing objects, the present invention solvesthe above-mentioned problems with respect to the magnetic domain controllayer by the following means, and provides a magnetoresistive sensorhaving excellent reproducing resolution, a magnetic head using the same,and a magnetic disk apparatus.

Conventionally, the magnetic domain control layer is arranged on thelower magnetic shield by employing a multi-layered structure ofinsulating layer/(metal underlayer)/hard magnetic metal materiallayer/insulating layer. In the present invention, there is used meanswherein the magnetic domain control layer comprises a single layer madeof a hard magnetic material having high electric resistivity, therebydirectly performing magnetic domain control. According to this method,the insulating layers arranged at the upper and lower sides of themagnetic layer can be omitted. Thus, when the magnetoresistive sensorlayer is made thinner, a loss of the susceptibility due to the thicknessof the insulating layer can be reduced, so as to lower the shunting lossof an electric current. In addition, since the magnetic domain controllayer is in direct contact with the magnetoresistive sensor layer, theloss of the magnetic field of the magnetic domain control can beminimized.

As a hard magnetic material having high electric resistivity with suchcharacteristics, there are (1) a magnetic oxide having a spinel lattice,and (2) a granular magnetic material made of a hard magnetic metalmaterial and a non-magnetic insulating material. With respect to (1),there is γ-Fe2O3 or the like. When a γ-Fe2O3 (004) layer grows, theresidual magnetization is relatively large, the coercivity is high, andthe specific resistance is high and 10⁵ to 10⁶Ωcm. Thus, this isadaptable to the above-mentioned single magnetic domain control layer.As for such a system, there is also γ-(FeCo)2O4.

However, in order to exhibit the magnetic characteristic by making thespinel lattice thinner, it is generally necessary to manufacture thelayer at a very high substrate temperature (above 500° C.). When thelayer is manufactured in a practical temperature range below 300° C.using a sputtering method, it tends to be an amorphous layer. As meansof solving this, there is envisaged a method of inserting one highorientation thin oxide film or one single crystal thin film, with anNaCl structure, under the spinel lattice magnetic layer, so as to formthereon the above-mentioned magnetic domain control layer having highelectric resistivity, and this is used as means.

Examples of the underlayer material for use in this method include CoO(200), MgO (200), NiO (200), EuO (200), FeO (200) and ZnO (001). Thesematerials can be relatively easily grown at room temperature by means ofthe sputtering method. When a spinel type compound γ-Fe2O3 is grown onthis plane, it is found that the γ-Fe2O3 (400) plane can be manufacturedon these oxides in a relatively low temperature range below 300° C.These thin oxide films can exhibit a function as the underlayer even inthe thickness range of 1 nm to 5 nm. These underlayers are electricallyan insulator to insulating semiconductor. Basically, they can eliminateshunting from the magnetoresistive sensor layer to the magnetic domaincontrol layer.

In the granular magnetic material made of a hard magnetic metal materialand a non-magnetic insulating material, the multi-layer laminated isformed using the mixed sputtering method or the sputtering method, sothat a hard magnetic material in granular form is formed in thenon-magnetic insulating material. At this time, when the granular volumeis smaller than the critical volume (granular volume V in which thermalenergy kT is larger than magnetic energy MV+KV), the material becomesmagnetically paramagnetic, or weak soft magnetic. However, when thegranular particle is larger than the critical volume and the granularshape is changed anisotropically for pinning by the insulator, it canbecome magnetically hard. The granular magnetic material of the presentinvention is a material in which the hard magnetic metal material isenclosed by the non-magnetic insulating material, and the granularvolume is larger than the critical volume. When the above-mentionedconditions are met, the granular shape is optional.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the sectional structure of the media-opposedsurface side of the magnetoresistive sensor of Example 1 of the presentinvention and the position of a magnetic domain control layer;

FIG. 2 is a cross-sectional view of the depth direction of themagnetoresistive sensor of Example 1 of the present invention;

FIG. 3 is a cross-sectional view of the media-opposed surface side ofExample 1 (3) of the present invention showing the position relationbetween the magnetic domain control layer having high electricresistivity and the magnetoresistive sensor layer;

FIG. 4 is a cross-sectional view of the media-opposed surface side ofExample 1 (2) of the present invention showing the position relationbetween the magnetic domain control layer having high electricresistivity and the magnetoresistive sensor layer;

FIG. 5 is a cross-sectional view of the media-opposed surface side ofExample 1 (1) of the present invention showing the position relationbetween the magnetic domain control layer having high electricresistivity and the magnetoresistive sensor layer;

FIG. 6 is a cross-sectional view of the media-opposed surface side ofExample 1 (4) of the present invention showing the position relationbetween the magnetic domain control layer having high electricresistivity and the magnetoresistive sensor layer;

FIG. 7 is a cross-sectional view of the media-opposed surface side ofExample 4 of the present invention showing the position relation betweenthe magnetic domain control layer having high electric resistivity andthe magnetoresistive sensor layer;

FIG. 8 is a diagram showing the sectional structure of the media-opposedsurface side of the magnetoresistive sensor of Example 5 of the presentinvention and the position of the magnetic domain control layer;

FIG. 9 is a cross-sectional view of the depth direction of themagnetoresistive sensor of Example 5 of the present invention;

FIG. 10 is a three-dimensional block diagram showing the structure ofthe exposed type magnetoresistive sensor of Examples 1 and 5 of thepresent invention;

FIG. 11 is a block diagram schematically showing one example of the yokestructure shown in Example 5 of the present invention and the positionof the magnetic domain control layers of the present invention tomagnetic domain-control this;

FIG. 12 is one example of the position of the magnetic domain controllayers of the yoke structure shown in Example 5 of the presentinvention;

FIG. 13 is one example of the position of the magnetic domain controllayers of the yoke structure shown in Example 5 of the presentinvention;

FIG. 14 is a block diagram schematically showing one example of the fluxguide type yoke structure shown in Example 5 of the present inventionand one example of the position of the magnetic domain control layers ofthe present invention to magnetic domain-control this;

FIG. 15 is a diagram showing one example of the shape of the flux guidetype yoke of Example 5 of the present invention, and one example of theposition relation between the same and the magnetoresistive sensor;

FIG. 16 is a diagram showing one example of the shape of the flux guidetype yoke of Example 5 of the present invention, and one example of theposition relation between the same and the magnetoresistive sensorlayer;

FIG. 17 is one example of the position of the magnetic domain controllayers of the yoke structure shown in Example 5 of the presentinvention;

FIG. 18 is one example of the position of the magnetic domain controllayers of the yoke structure shown in Example 5 of the presentinvention;

FIG. 19 is a schematic diagram of the structure and operation of amagnetic disk apparatus of Example 6 of the present invention;

FIG. 20 is a side view of one example of the structure of MRAM using themagnetoresistive sensor layer provided with the magnetic domain controllayers having high electric resistivity of the present invention;

FIG. 21 is a diagram of FIG. 20 viewed perpendicular to the substratesurface (representing state “1”); and

FIG. 22 is a diagram in which the direction of an electric currentflowing through the conductive line is shifted 90 degrees from that ofFIG. 21 (representing state “0”).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described based on theexamples with reference to the drawings.

Example 1

FIGS. 1 and 2 are diagrams showing the structure of a magnetoresistivesensor as one embodiment according to the present invention viewed fromthe media-opposed surface and section of the plane perpendicular to thedepth direction, respectively. Arrow 110 in the drawing denotes thedepth direction.

On a substrate 101 is formed a base insulating layer 102, made of, forexample, alumina. After subjected to precision polishing by means ofchemimechanical polishing (CMP), a lower magnetic shield layer 103 isformed thereon. This is made of Ni81Fe19 having a thickness of 2 μmmanufactured by, for example, the sputtering method, the ion beamsputtering method, or the plating method. A resist mask is patterned ina predetermined size in this layer, and other portions thereof aresubjected to ion milling to strip off the resist. Al2O3 is grown thereonto fill in portions 104 removed by ion milling. After this is subjectedto CMP, an electrode layer made of Cu or Ru (not shown) is grown by 20nm, so as to form a drawing electrode layer 111 in a portion away fromthe sensor portion. This is, for example, a layer made of Ta, Au and Ta.

A lift-off pattern is formed in a region on the previous electrode layerconsisting of a magnetoresistive sensor layer, so as to form thereon alayer having a thickness of 150 nm made of a mixture of Al2O3 and SiO2.This may be a single phase layer made of Al2O3 or SiO2. After liftingthis off, a magnetoresistive sensor layer 105 is formed, and a layer 108(e.g., FIG. 2) is formed on top of electrode layer 111. In themagnetoresistive sensor layer, there are studied as the examples twotypes of using GMR and of using TMR. An electric current for sensing asignal (sensing current) is flowed perpendicular to the plane of thesemagnetoresistive sensor layers (Current Perpendicular to the Plane:CPP).

A GMR layer comprises, for example, from the lower side, a Co48Mn52anti-ferromagnetic layer of 12 nm, a pinned layer consisting of Co of 1nm, Ru of 0.8 nm and Co of 2 nm, a free layer consisting of Cu of 2 nm,Co of 0.5 nm and Ni81Fe19 of 2.5 nm, and Ta of 3 nm. With respect to theanti-ferromagnetic layer, in the case of using a regularanti-ferromagnetic layer of a PtMn system, anneal is required in orderto exhibit the exchange bonding between the pinned layer and theanti-ferromagnetic layer. The magnetic field of the pinned layer isdirected in the in-plane direction orthogonal to the depth.

On the other hand, a TMR layer comprises, for example, from the lowerside, a free layer consisting of Ta of 5 nm, NiFe of 3 nm and a CoFelayer of 2 nm, a barrier layer consisting of Al2O3 of 2 nm, a pinnedlayer consisting of CoFe of 2 nm, Ru of 1 nm and CoFe of 1 nm, aanti-ferromagnetic layer consisting of MnIr of 10 nm, Ta of 3 nm, andNiFe of 5 nm.

After forming the magnetoresistive sensor layer 105, a lift-off materialis formed in the position as an active region (on the layer served bothas the lower shield and electrode). Then, the magnetoresistive sensorlayer is etched, for example, by the ion milling method. After etching,magnetic domain control layers 106 are formed so as to remove thelift-off mask. Thereafter, a pattern in the depth direction of themagnetoresistive sensor layer 105 is formed in the magnetic domaincontrol layers 106, and then, the portion therearound is removed by theion milling. A mixed layer of Al2O3 and SiO2 having a thickness of 150nm is formed thereon as a protective insulating layer 107 to define anupper shield layer 112.

A write element having a magnetic core laminated through a recording gapis formed on the magnetoresistive sensor to define a magnetic head ofthe magnetic disk apparatus.

By means of a method represented by the above-mentioned manufacturemethod, the magnetoresistive sensor of the present invention and themagnetic head using the same are manufactured. In this, the magneticdomain control layer 106 has a required characteristic different fromthe case of flowing an electric current in the plane. In the magneticdomain control layer, there have been studied the magnetic domaincontrol layer itself is: (1) a layer made by laminating, from the lowerportion, an insulating layer Al2O3—SiO2 layer of 220 nm, a Cr underlayerof 5 nm, a magnetic layer CoCrPt of 25 nm, and an insulating protectiveAl2O3—SiO2 layer of 220 nm on the top, (2) a layer made by laminating,as the magnetic layer, a CoO underlayer of 5 nm, and a γ-Fe2O3 layer of50 nm, (3) a layer made by laminating, as the magnetic layer, a γ-Fe2O3layer of 50 nm, and (4) a layer by alternately laminating CoCrPt of 1.5nm and SiO2 of 1.1 nm (60 nm thick).

In the method (1), there is shown a conventional magnetic domain controllayer as shown in the schematic structure of FIG. 5, as a comparativeexample. When the conventional magnetic domain control layer is appliedas-is, the gap between the shields Gs not less than 70 nm makes itpossible to manufacture magnetic domain control layers 501, 502 and 503.However, the following points in formation of the junction of the endsof the magnetoresistive sensor layer are important in order to maintaininsulation of the CoCrPt (502) from the lower portion Al2O3 (501).

One of the points is that, in order to maintain insulation, the ends ofthe magnetoresistive sensor layer 105 must be completely coated by theAl2O3 layer 501, the hard metal magnetic CoCrPt (502) must be grownthereon, and the Al2O3 layer 503 grown thereon must completely coat theCoCrPt layer. For this reason, the sputtering apparatus forming thelayer needs to have a characteristic such that the Al2O3 is insertedinto the lift-off pattern in the plane, and CoCrPt is not inserteddeeply therein, and to ensure such manufacture conditions. Further, formanufacture, the lift-off pattern must be formed, and when the size ofthe sensor is reduced (not more than 1 μm), the formation thereof isdifficult. The insulating layer having a thickness less than 20 nmcannot have sufficient insulation properties, and when the layer isthick in order to maintain the sufficient insulation properties, the gapbetween the end of the magnetoresistive sensor layer 105 and the CoCrPtlayer as the magnetic domain control layer is larger, so that themagnetic domain control force is weak, thereby making magnetic domaincontrol impossible. For this reason, when the gap between the shields isnot more than 70 nm in order to make the resolution of the read headhigh, the method (1) is difficult to use.

The method (2) is one embodiment of the present invention shown in FIG.4. First, a lower shield 302 is formed on an appropriately treatedsubstrate 301, and the region in contact with opposite ends of themagnetoresistive sensor layer 105 thereon is formed with a CoOunderlayers 304. CoO (002) is grown in the CoO underlayer, and γ-Fe2O3(65 nm) is formed thereon, so as to manufacture a magnetic domaincontrol layer 303. γ-Fe2O3 has a (004) orientation plane by the effectof the underlayer. This is the same for Co-γ-Fe2O3 as other ferrite.

This layer has a specific resistance not less than several 10 Ωcm in thelayer state. In this case, the layer requires no lift-off pattern, andcan be manufactured by the usual resist pattern. The magnetoresistivesensor layer may be in contact with the magnetic domain control layer,or the magnetic domain control layer may be lifted on themagnetoresistive sensor layer. According to this method, the magneticdomain control layer has electric resistivity much higher than themagnetoresistive sensor layer. A signal sensing current flows onlythrough the magnetoresistive sensor layer, so as to eliminate a loss ofthe signal intensity due to shunting to the magnetic domain controllayer.

Even when the gap between the shields is smaller, the insulatingprotective layer of conventional type is unnecessary. According to this,it is possible to reduce the total thickness of the magnetic domaincontrol layer causing an equivalent susceptibility. The susceptibilityis an amount to determine the thickness of the magnetic domain controllayer by multiplying the magnetization of the free layer of themagnetoresistive sensor layer by the thickness thereof. In the case ofthe magnetic domain control layer, multiplication of the residualmagnetization by the thickness is equivalent to this. γ-Fe2O3 orCo-γ-Fe2O3 in this study has a high specific resistance of 10⁵ to 10⁶Ωcm, a coercivity of about 1.3 to 5.0 kOe, a residual magnetization of1.2 to 3.5 kG, and a saturated magnetization of 3.5 to 4.2 kG. Thesevalues are smaller than those of CoCrPt (having a coercivity of about1.0 to 3.0 kOe, a residual magnetization of 4 to 9 kG, and a saturatedmagnetization of 6.5 to 12.0 kG). In consideration of the protectiveinsulating layer, it is effective for the magnetic domain control whenthe gap between the shields is small. As the layer formation process,the conventional four layers (Al2O3/Cr/CoCrPt/Al2O3) can be reduced totwo layers, so as to make the operation efficient.

In the method (3) as another example of the present invention, FIG. 3shows a basic construction. This is the same as the method (2) exceptthat the oxide underlayer 304 of the magnetic domain control layer isabsent. In view of the manufacture method, the point of directly formingγ-Fe2O3 is different. In this case, the substrate temperature is raisedto 300 to 500° C., and then, the layer is formed by the high vacuumlayer forming apparatus having a maximum degree of vacuum of 10⁻¹¹ Torr,or the top surface of the lower shield exposed is irradiated with anoxygen ion using an ECR ion source to oxidize the surface, so thatγ-Fe2O3 can be precedably grown. In this case, the same effect as in themethod (2) is found to be given.

The method (4) as another example of the present invention has thestructure of FIG. 6. A magnetic domain control layer 601 in this case isa layer by alternately laminating CoCrPt of 1.5 nm and SiO2 of 1.1 nm.The thickness ratio of CoCrPt/SiO2 is between 2:1 and 1:2, CoCrPt has alayer thickness of 0.5 to 2 nm, a specific resistance not less than 10mΩcm, a coercivity not more than about 1.0 kOe, and a residualmagnetization of 2 to 4 kG, so as to give the same effect as describedabove. However, in this case, it is more effective that Al2O3 not lessthan 10 nm is inserted for the underlayer.

In the methods (2) to (4) of this example, even when the gap between theread shields (gap distance) is not more than 70 nm, the readcharacteristic is not found to be deteriorated due to the conduction ofthe magnetoresistive sensor layer and the magnetic domain control layer.

Example 2

The magnetoresistive sensor in Example (1) described above has thestructure by lamination from the lower portion. The structure in whichthe upper and lower portions are reversed can also give the same effect.

Example 3

In Example (1) described above, in formation of the magnetic domaincontrol layer using a spinel type oxide such as γ-Fe2O3, on theunderlayer 304 of the magnetic domain control layer 303, is formed, inplace of the CoO layer, an oxide layer having a crystal structure ofNaCl type such as Mg (200), NiO (200), EuO (200), FeO (200) or ZnO (200)as well as a (200) plane. Then, the spinel ferrite formed thereon can becrystallized at low temperature. As a method of forming this layer,there is a method of manufacturing these layers by the sputteringmethod, the ion beam sputtering method or the cluster ion beam method.As a method other than this, on the lower shied 302 a layer of Co, Mg,Ni, Eu, Fe or Zn is formed in a thickness of 1-5 nm. This layer isexposed to oxygen in vacuum, is irradiated with oxygen using ECR plasma,or is exposed to low-pressure oxygen by heating the substrate (100 to250° C.) so as to form an oxide layer, thereby forming a spinel ferritethereon. This method can give equivalent results.

As a spinel type oxide formed on the oxide underlayer 304, there areγ-Fe2O3 and Co-γ-Fe2O3. The latter is thought to be a solid solution ofγ-Fe2O3 and CoFe2O3, and is represented by the chemical formula(Co(y)Fe(8-2y)/3)O4(γ-Fe2O3). The ratio of Co is varied to change thecoercivity. As compared with the case that these are formed on a glasssubstrate, a high coercivity increased 1.5 to 2 times is exhibited inthe same thickness as that of these formed on the oxide underlayer, andwhen the Co/Fe ratio is 0.08, a coercivity of 2.6 kOe in 10 nm.

Example 4

Before forming the magnetic domain control layer of Example 1 (1), asshown in FIG. 7, portions 701 are formed with MnZn ferrite as a softmagnetic layer having high electric resistivity, an insulator and ametal magnetic material are alternately laminated, or there is formed agranular layer in which these are sputtered at the same time into amixed state, for example, a layer by laminating, by 25 number of layers,Co90Fe10 layers having a thickness of 1.4 nm and Al2O3 layers having athickness of 1.0 nm. Thereafter, the outside of the layer is removed bythe ion milling in the position several mm away from the outerperipheral portion of the magnetoresistive sensor layer, and then metalmagnetic layers such as CoCrPt as represented by 502 are formed in theremoved portions. This structure has no shunting since the metalmagnetic domain control layers 502 are not in direct contact with themagnetoresistive sensor layer. However, since a layer with soft magneticproperties is disposed therebetween, the magnetic field of the magneticdomain control is effectively applied to the magnetoresistive sensorlayer.

Example 5

In the magnetoresistive sensor with the magnetoresistive sensor layer isexposed, according to a three-dimensional schematic diagram explodingthe structure of the magnetoresistive sensor, as shown in FIG. 10, themagnetic domain control layers 106 are arranged on opposite ends of themagnetoresistive sensor layer 105, and the magnetic shields 103 and 109are disposed at the upper and lower sides thereof. In the presentinvention described in the above examples, the layer 106 is a materialhaving high electric resistivity. There is a magnetoresistive sensor ofanother structure, that is, a magnetoresistive sensor provided with ayoke structure as the write sensor. FIG. 11 is a three-dimensionaldiagram schematically showing a representative yoke structure and themagnetic domain control layer. In this structure, a magnetoresistivesensor layer 1105 is not exposed from the surface opposite the media. Inthe gap between a lower magnetic shield 1103 and an upper magneticshield 1107, made of Ni81Fe19, are arranged yoke layers made of asimilar soft magnetic material. The properties of this structuredescribed below are observed. In FIG. 11, the yoke layers in C ring formconsist of an upper yoke 1106 joined to a lower yoke 1102. Other thanthis, the lower yoke is reduced on the end thereof, or has a thick film,or the yoke is discontinuous under the magnetoresistive sensor layer. Inthe diagram, a magnetic domain control layer 1101 is shown. The magneticdomain control layer having high electric resistivity shown in Example 1of the present invention is used as the layer. This magneticdomain-controls at least the lower yoke and the magnetoresistive sensorlayer and has no shunting in the periphery. The magnetic domain controllayer has a type for magnetic domain-controlling the upper and loweryoke layers and the magnetoresistive sensor layer at the same time, anda type for magnetic domain-controlling each. In either structure, it isfound that the good magnetic domain control is possible withoutshunting.

The above-mentioned FIG. 11 is a block diagram for simply showing theposition of the magnetic domain control layer in the yoke structure. Indetail, the magnetic domain control layer is manufactured in a structureof the magnetoresistive sensor layer as one example of the presentinvention viewed from the media-opposed surface and a structurerepresented by the diagram showing a section of the depth direction, asshown in FIGS. 8 and 9.

FIG. 14 shows a schematic diagram of the flux guide type yoke structureand the magnetic domain control thereof. The surface viewed from the XYside in the diagram is the media-opposed surface. On themagnetoresistive sensor layer disposed on the lower shield 1002 so as tobe recessed, is formed a soft magnetic layer made of, for example,Ni89Fe19, as indicated by 1401, having a shape, which extends from theposition exposed from the media-opposed surface onto themagnetoresistive sensor layer, is in contact with the surface oppositethe media-opposed surface of the magnetoresistive sensor layer, andextends to a depth direction Z. This layer guides the magnetic flux fromthe recording media to the magnetoresistive sensor layer, and is calleda flux guide. In order to magnetic domain-control this flux guide layer,in the process of forming the magnetoresistive sensor layer, ionmilling, patterning, forming the flux guide layer 1401, and forming themagnetic domain control layer 1001, the magnetic domain control materialhaving high electric resistivity of the present invention is used as themagnetic domain control layer 1001 to give the following advantages.Conventionally, the insulating protective layer must be formed in thetrack width direction of the magnetoresistive sensor layer. In thepresent invention, even when the magnetic domain control layer is formeddirectly, magnetic domain control is possible without shunting. In theflux guide type yoke structure, it is also possible to magneticdomain-control the magnetoresistive sensor layer together with the fluxguide type yoke.

As shown in FIGS. 15 and 16, in order to increase an amount of themagnetic flux sensed by the magnetoresistive sensor layer, the portionin contact with the magnetoresistive sensor layer of the yoke isdiscontinuous. In such a structure, the material of the magnetic domaincontrol layer is a layer having high electric resistivity so as to formthe magnetic domain control layer of the present invention. Examples ofarrangement of the magnetic domain control layer of the yoke structureof this embodiment are shown in FIGS. 17 and 18.

Example 6

FIG. 19 is a diagram showing the magnetic disk apparatus of oneembodiment using the magnetic head mounting the magnetoresistive sensoraccording to the present invention.

The magnetic disk apparatus illustrated comprises a magnetic disk 1901as a magnetic recording media formed in disk form for recording data ina recording region called a concentric track and a magnetic transducer,a magnetic head 1906 comprising a magnetic transducer, reading andwriting the data and mounting the magnetoresistive sensor according tothe present invention (in detail, comprising a magnetic head 1910 and aslider 1909), actuator means 1911 for supporting the magnetic head 1906to move it to a predetermined position on the magnetic disk 1901, andcontrol means for controlling transmission and receive of data by readand written by the magnetic head and movement of the actuator means.

The structure and operation will be described below. At least onerotatable magnetic disk 1901 is supported by a rotation axis 1902, andis rotated by the drive motor 1903. At least one slider 1909 is placedon the magnetic disk 1901, one or more sliders 1909 are disposed, andsupport the magnetic head 1910 according to the present invention forread and write.

The magnetic disk 1901 is rotated, and at the same time, the magnetichead 1906 is moved on the disk surface for access to a predeterminedposition in which data to be desired are recorded. The magnetic head1906 is provided on an arm 1908 by a gimbal 1907. The gimbal 1907 hasslight elasticity and brings the magnetic head 1906 into contact withthe magnetic disk 1901. The arm 1908 is mounted on the actuator 1911.

There is a voice coil motor (hereinafter referred to as VCM) as theactuator 1911. VCM consists of a movable coil placed in the magneticfield fixed, and the movement direction and movement speed of the coilare controlled by an electric signal given from the control means 1912through a line 1904. The actuator means of this embodiment comprises,for example, the magnetic head 1906, the gimbal 1907, the arm 1908, theactuator 1911 and the line 1904.

During operation of the magnetic disk, the magnetic disk 1101 is rotatedto cause air bearing due to air flow between the magnetic head 1906 andthe disk surface, which lifts the magnetic head 1906 from the surface ofthe magnetic disk 1901. During operation of the magnetic disk apparatus,the air bearing is balanced with the slight elasticity of the gimbal1907, the magnetic head 1906 is not in contact with the magnetic disksurface, and is maintained so as to be lifted from the magnetic disk1901 at a constant interval.

The control means 1912 generally comprises a logic circuit, memory, andmicroprocessor. The control means 1912 transmits and receives a controlsignal through each line, and controls various structure means of themagnetic disk apparatus. For example, the motor 1903 is controlled by amotor driven signal transmitted through the line 1904.

The actuator 1911 is controlled so as to optimally move and position, bymeans of a head position control signal and a seek control signalthrough the line 1904, the magnetic head 1906 selected to a data trackto be desired on the magnetic disk 1901 associated therewith.

The magnetic head 1910 reads data on the magnetic disk 1901 so as toconvert the data to an electric signal. The control signal receives anddecodes the electric signal through the line 1904. In addition, anelectric signal written as data to the magnetic disk 1901 is transmittedthrough the line 1904 to the magnetic head 1910. In other words, thecontrol means 1912 controls transmission and receive of information reador written by the magnetic head 1910.

The read and write signals described above permit means directlytransmitted from the magnetic head 1910. There are, for example, anaccess control signal and a clock signal as the control signal. Themagnetic disk apparatus may have a plurality of magnetic disks andactuators, and the actuator may have a plurality of magnetic heads.

Such plurality of mechanisms are provided, so as to form the so-calleddisk array apparatus.

In this apparatus, the magnetoresistive sensor of the present inventionis used as the magnetoresistive sensor of the magnetic head. It is thuspossible to improve reproducing resolution of the apparatus according toimproved performance of the magnetoresistive sensor.

Example 7

FIG. 20 shows a representative structure of an already known MRAM as oneexample of the magnetic recording sensor. The magnetic recording sensorhas a structure comprising a plurality of cells in parallel including amagnetoresistive sensor layer 2002 for recording information, a bit line2001 connected to the magnetoresistive sensor layer for flowing anelectric current 2003 to the sensor, a word line 2005 (with current2006) in the position opposite the bit line 2001 by interposingtherebetween the magnetoresistive sensor layer 2002 and in the positionaway from the magnetoresistive sensor layer 2002 for performingrecording operation onto the magnetoresistive sensor layer orthogonallyto the bit line, an amplifying system for amplifying a read signal, anda read conductive line 2007 (supported by structures 2004, 2009) forswitching between read and write, wherein the magnetoresistive sensorlayer 2002 comprises the magnetoresistive sensor layer as shown inExample 1. Since an electric current flows perpendicular to the plane,the use of the magnetoresistive sensor layer is similar to that ofExample 1. The magnetoresistive sensor layer has the size consisting ofone side of 0.2 to 0.25 μm. The magnetization of the free layer of themagnetoresistive sensor layer is rotated in the direction of an electriccurrent flowing through the word line and the bit line, by varying thedirection of the synthetic magnetic field caused in the magnetoresistivesensor layer portion. When the magnetization direction of the free layerof the magnetoresistive sensor layer is rotated and the magnetic domainis caused in the free layer, the resistance value to the magnetic fieldis varied to lower the S/N ratio, so that memory cannot be read. Inorder to controllably perform this, the magnetic domain control layer isrequired. Magnetic domain control layers having high electricresistivity 2008 devised in the present invention are positioned onopposite ends of the magnetoresistive element layer 2002. Thus, magneticdomain control is possible without loss of shunting to the magneticdomain control layer, so as to improve the recording density of themagnetic recording sensor.

According to the present invention, in the magnetoresistive sensor usingthe magnetoresistive sensor layer, (1) a loss of shunting to themagnetic domain control layer can be eliminated, (2) the number ofconventional processes for manufacturing the magnetic domain controllayer can be reduced, and (3) magnetic domain control can be conductedfinely by making the gap between the shields smaller since the thicknessof the magnetic domain control layer can be reduced by the size of thepressure-resistant protective layer. Accordingly, (4) themagnetoresistive sensor flowing an electric current perpendicular to theplane can provide the magnetic domain control layer practicable.Further, the magnetoresistive sensor of the present invention is used toprovide the magnetic head having excellent reproducing resolution andthe magnetic disk apparatus.

1. A magnetic recording sensor having a structure comprising a plurality of cells in parallel including a magnetoresistive sensor for recording information, a bit line connected to the magnetoresistive sensor for flowing an electric current to the sensor, a word line in the position opposite the bit line by interposing therebetween the magnetoresistive sensor layer and in the position away from the magnetoresistive sensor layer for performing recording operation onto the magnetoresistive sensor layer orthogonally to the bit line, an amplifying system for amplifying a read signal, and a read word line for switching between read and write, wherein the magnetoresistive sensor comprises the magnetoresistive sensor layer, and a layer for magnetic domain-controlling the magnetoresistive sensor layer is provided with the magnetic domain control layer having high electric resistivity according to any one of the magnetoresistive sensor including a substrate, a pair of magnetic shield layers consisting of a lower magnetic shield layer an an upper magnetic shield layer, a magnetoresistive sensor layer disposed between the pair of magnetic shields, an electrode terminal for flowing a signal current perpendicular to the plane of the magnetoresistive sensor layer, and magnetic domain control layers for controlling Barkhausen noise of said magnetoresistive sensor layer, wherein said magnetic domain control layers disposed on opposite ends of the magnetoresistive sensor layer in a region from an end surface of a media-opposed surface side of the magnetoresistive sensor layer to a depth position are made of a material having a specific resistance not less than 10 mΩcm, and are in contact with at least opposite end surfaces of said magnetoresistive sensor layer in said region.
 2. A magnetic recording sensor comprising: a plurality of cells in parallel including a magnetoresistive sensor for recording information; a bit line connected to the magnetoresistive sensor for flowing an electric current to the sensor; a word line in the position opposite the bit line by interposing therebetween the magnetoresistive sensor layer and in the position away from the magnetoresistive sensor layer for performing a recording operation onto the magnetoresistive sensor layer orthogonally to the bit line; an amplifying system for amplifying a read signal; and a read word line for switching between read and write, wherein the magnetoresistive sensor comprises the magnetoresistive sensor layer, and magnetic domain control layers disposed on opposite ends of the magnetoresistive sensor layer, and said magnetic domain control layers have a compound having composition of R₂O₃ containing at least R (R=Fe, Co, Mn, and Ni) and oxygen (O) and has a spinel lattice and a (400) orientation plane.
 3. A magnetic recording sensor according to claim 2, wherein a material consisting of a oxide underlayer of said magnetic domain control layer is a compound of RO consisting of at least R(R=Co, Mg, Ni, Eu Fe, and Zn) and oxygen (O) and has a NaCl structure and a (200) orientation plane, and a material consisting of said magnetic domain control layer on the oxide underlayer is a compound having a composition of R₂O₃ containing at least R (R=Fe, Co, Mn, and Ni) and oxygen (O) and has a spinel lattice and a (400) orientation plane.
 4. A magnetic recording sensor according to claim 2, wherein magnetic domain control layer comprises the compound layer disposed in contact with opposite ends of said magnetoresistive sensor layer, an a hard magnetic layer disposed outside the same, and said hard magnetic layer is made of a metal magnetic material having as the composition elements Co (cobalt), Cr (chromium), Pt (platinum), Ta (tantalum), and Ni (niobium).
 5. A magnetic recording sensor comprising: a plurality of cells in parallel including a magnetoresistive sensor for recording information; a bit line connected to the magnetoresistive sensor for flowing an electric current to the sensor; a word line in the position opposite the bit line by interposing therebetween the magnetoresistive sensor layer and in the position away from the magnetoresistive sensor layer for performing recording operation onto the magnetoresistive sensor layer orthogonally to the bit line; an amplifying system for amplifying a read signal; and a read word line for switching between read and write, wherein the magnetoresistive sensor comprises the magnetoresistive sensor layer, and magnetic domain control layers disposed on opposite ends of the magnetoresistive sensor layer, said magnetic domain control layers have a material that is granular layer made by mixing a hard magnetic material having high coercivity made of a metal magnetic material having as the composition elements Co (cobalt), Cr (chromium), Pt (platinum), Ta (tantalum), and Nb (niobium) with an insulating material made of Al₂O₃, SiO₂, HfO₂, TaO₂, TiO₂, Ta₂O₅, AIN, AISiN, or ZrO₂.
 6. A magnetic recording sensor according to claim 5, wherein magnetic domain control layer comprises the granular layer disposed in contact with opposite ends of said magnetoresistive sensor layer, and a hard magnetic layer disposed outside the same, and said hard magnetic layer is made of a metal magnetic material having as the composition elements Co (cobalt), Cr (chromium), Pt (platinum), Ta (tantalum), and Ni (niobium). 